Protein fluorescence explored for cataract diagnosis
Fluorescence of lens proteins could help understand, diagnose, and treat cataracts, researchers say.
“Rather than waiting for the condition to appear, it could be possible to diagnose and monitor cataract before it forms, allowing preventative measures to be taken where possible,” said Rory Duncan of Heriot-Watt University in Edinburh, United Kingdom in a press release.
Duncan and colleagues published their findings in Nature Scientific Reports.
The research focuses on post-translational modifications (PTMs) of Trp and Arg amino acid residues that accumulate as lenses age.
Current cataract diagnosis depends on light scattering methods which can detect defects in the lens structure when they reach at least 0.5 µm, the optical wavelength. But the formation of PTMs may precede the micron-sized defects that make these light-scattering methods possible.
Matured eye lens fibre cells do not contain organelles apart from the proteasome, Duncan and colleagues point out. This gives the eye lens optical homogeneity and minimizes Rayleigh scattering. But it also precludes the synthesis of new proteins.
As a result, proteins synthesised in new cells remain throughout the lifespan of mature cells. Without protein turnover, PTMS accumulate in crystallins, resulting in protein misfolding and aggregation and causing light scattering.
Also, some PTMS absorb light in the visible spectral range, reducing lens transparency and giving rise to coloration.
Modifications of Trp side chains can change the position of the Trp emission spectrum and fluorescence. So the researchers hypothesized that formation PTMs in crystallins endows the eye lens a unique fluorescence “signature” that could be measurable.